The spread of the Internet enables people to access various information through Web pages. Search engines heavily contribute to such accesses to the information. The search engines automatically collect (i.e. clone) information dispersively held in the Internet to generate indexes for collected information, and provides them for information searchers. Because an information provider side's object of opening information on the Web pages to the public is to distribute and deliver the information, it is basically preferable that the search engines clone the information to generate indexes for it. Commercially, there is a case where the competition to obtain the higher ranking in the search engine is carried out for a specific keyword.
However, the Web pages include contents provided to be intrinsically opened to the public and information to be collaterally opened to the public, such as information concerning an origin of the contents or a contact address. There is no problem that the contents provided to be intrinsically opened to the public are cloned by the search engines. However, when the information concerning the origin of the contents or the contact address is cloned, there is a case where a problem occurs. For example, although there is a case where a mail address as the information concerning the contact address is opened to the public, the mail address may be cloned for the target of the spam mail. In addition, also as for the information concerning the origin of the contents, when the name and address are cloned, they may be used for various crimes. Other information may include data that is not preferable for allowing machines such as the search engines to clone it and allowing the secondary use of it.
Therefore, as the countermeasure for the mail address, there is a case where a method of converting hoge@hoge.com, which is an example of the mail address, into a character string such as “hoge at hoge dot com”, or a method of inserting spaces is adopted. However, although such methods can be adopted for the mail address or telephone number, there is no method of converting information such as the name or address, and incorrect information may be distributed.
In addition, for example, JP-A-H6-348808 discloses a technique to output all index information including index information for a secret document, important document or the like on a index sheet so as to easily understand it, and to enable the confidentiality to be held. Specifically, the index information and image data of the document are read out from a storage medium to check whether or not a specific character string is included in the image information or it has a special file attribute. When either condition is satisfied, a special pattern such as a character pattern “secret” or “important” is synthesized into the index image or only the special pattern instead of the index image is expanded and disposed onto an output buffer, and the data is sent to a printer to form image onto a paper. Therefore, the index sheet is output. This technique outputs the special pattern for data whose secrecy has to be held. However, it cannot convert the data whose secrecy has to be held into data that can be recognized by the human being but cannot be recognized by machines.
As described above, it is impossible for the conventional technique to correctly inform the human being of content of the contents but to prevent from cloning and secondarily using part of the contents whose distribution is not desired by the information provider.